Heat treating furnace



Filed Feb. 16. 193s INVENTOR K.A. STEVENSON ATTORNEY Patented oct. s, 1940 UNITED STATES PATENT oFFlcEf This invention relates to a heat treating furnace, and has forfan object` to provide an im,- proved heat treating furnace especiallysuitable for heat treatment of high tensile aluminum alloys, as well as duraluminum. .l

In the heat treatment of duraluminum there are three very importantffactors necessary to the optimum success. A'l'hese factors are accurate `contro-1 of the temperaturauniform temperature I l0 throughout the furnace and rapid cooling from the heat treatment temperature so as to.y obtain maximumv resistance to corrosion and tensile strength of the product. i

The furnace of thislinventionis especially intended for use in heat treating duraluminum rivets, but of course is equally usable, for heat I treating other aluminum alloy products which are of a size that they may be convenientlyplaced in the furnace. One of the advantages of this previously possible. Although salt is used as a heating medium, `it doeswnot come into actual contact with the products being treated, and it is therefore no-t necessary to drain off the salt when the heating is stopped and the quenching takes place. The quenching is therefore more rapid and more effective, and the results are more accurate.

With the foregoing and other objects in View,

bination and arrangement-of parts as hereinafterv described and illustrated in the drawing, in which: s, i

Figure 1 is a front elevational view of the furnace of this invention; and a Fig. 2 `is a sectional View online 2-2 of Fig..1. There is shown at lIl `the furnace of this. invention mounted on supporting legs Il including sheet metal walls I2 and a'removable cover i3. Within they walls I2 there is provided refractory fire brick I4, within which is supported a chamber I5.` Extending intothe bottom of this chamber I5 i"s a pair of electrical heating elements I6 receiving their current supply from conductors I1 connected at I8 to any suitable source of electricity. The front ,wall I9 is provided with insulation materialZ, which insulation material 20 is likewise provided in the top cover I3. Extending through the front wall I9 and into the chamber I5 are a plurality of cylindrical tubes ZI, vseven being shown in this in-` stance, these tubes 2I being made of metal or other good heat conducting material.

A supply of salt 22 placed in chamber I5 entrely surrounds the cylindrical` tubes 2| and furnace is a closer temperature control than the invention consists inthe construction, com' serves as a heat conductor fory transmitting the heat supplied by the electrical heating elements I6 to the tubes `2l and to cylinder drawers 23 which are placed therein. A thermo-couple 24 extends into the salt 22 within the chamber I5 for measuring the temperature and may be con- Y nected to automatic controls for regulating the temperature. Y

4The draw-ers 23, as shown, are provided with handle pulls 25, which, it will be observed, extend in a setdirection, showing that the drawer is in proper position for containing the duraluminum rivets or other products `2'5 within the semi-cylindrical drawer portion 2'I thereof, and insulated portion 28 lled with the same insulation material 2li connects the same cylindrical drawer portion v2l to the handle pull 25.

l The furnace I0 may be provided with any con- A quench tank 29 which may be iilled with a Y cooling medium such as water, has a supply pipe 30 and control valve 3I at one end thereof, and an overow drain and pipe 32 at the` other end thereof, the quench` tank 29 being supported at the front of the furnace III by braces 33 just below the mouth of the cylindrical tubes 2|.

A foraminous cup 34, supported by a iiange 35 through an opening in a plate 36, extends into the quenching medium in the tank 29, a removable funnel 31 being provided for the cup 34 located directly beneath the mouth of the tube 2|, there being one cup and funnel for each tube.

In operation, the'alloys or other products 26 to be heat treated yare placed in the drawers 23 and inserted into the tubes 2 I, chamber I5 being lled with salt. The currentv is turned on and the temperature is controlled according to the temperature indicated by the thermo-couple 24. The salt liquefies and transmits a uniform degree of heat through the tubes 2| to the products 26 within the drawer portion 21. When theheating has been continued for the predetermined period necessary, the drawers arerotated and withdrawn, spilling the products 26 through the a products 26, and hence it is not necessary to drain the salt oif the products or rinse the products 26 before they are placed in the quench, and there is no salt present to retard the speed of the quench. The products may be removed from exposure to the heat of the furnace to the foraminous cup within the quench in a period of less than two seconds, thus preventing the lossr of heat between the furnace and the quench, which loss of heat tends to destroy some of the corrosion resistance, and to lower the tensile strength of th product.

Other modifications and changes in the proportions and arrangements of the parts may be made by those skilled in the art Without departing from the nature of the invention, Withinthe scope of what is hereinafter claimed.

The invention described herein may be manufactured and used by or for the Government of the United States of vAmerica for governmental purposes without the payment of any royalties thereon' or therefor. f

Having thus set forth and disclosed the nature of this invention, what is claimed is:

l. As an article of manufacture, al heat treatment furnace comprising a heating chamber, a heat source for said chamber, a tubular heating chamber extending into saidl heating chamber from one side thereof, a fusible salt Within said heating chamber encompassing said tubular heating chamber and transmitting heat from said heat source to said tubular heating chamber, a product-container tubular insert extendable into andretractable from said tubular heating chamber, said insert being open on one side thereof .to receive or discharge products to be heat treated therein, said tubular heating chamber pre- -Venting the fusible salt from, contacting the products, handle means on said insert without said heating chamber for rotating and withclrawing said insert, said insert being rotatable to discharge the products therein through the quench means including a quench tank, and means extending into said quench tank for receiving the products discharged from the open sides of said insert and exposing the products to the quenching effects of the quench tank, whereby said insert may be rotated and retracted to quickly remove the products from the heating chamber to the quench tank in less than two seconds.

2. As a new article of manufacture, means for Yheat treating small aluminum alloy products at a uniform temperature for a desired period of time and for removing the heat treated products from the heat treatment to a quench means Within a period of less than two seconds to minimize loss of corrosion resistance, said means comprising a comparatively large heating chamber, a heat source within said chamber, a comparatively small unperforated tubular heating chamber extending into said large heating chamber from one side thereof, said large heating chamber containing a fusible salt encompassing said small tubular heating chamber for transmitting heat from said heat source to said small tubular heating chamber, said small tubular heating chamber excluding said fusible salt from the inside thereof, a product-container tubular insert extendable into and retractable from said small tubular heating chamber, said insert being open on at least one side thereof to receive or discharge the aluminum alloy products to be heat treated therein free from contact with the fusible salt, means on said tubular insert for withdrawing and rotating said insert to discharge the products therein through the open side, and quench means immediately Without said heating chamber and below the path of said tubular insert as it is retracted whereby said insert may be retracted and rotated tol quickly remove the products from the heating chamber to the quench means.

KENNETH A. STEVENSON. 

